Hydrofluoric acid alkylation process



Sept. 28, 1948. F. E. FREY 2,450,038

HYDROFLUORIC ACID ALKYLATION PROCESS Filed Aug. 10, 1943 A TTORNEYS' Pltenied Sept. 28, 1948 UNITED .STATESI PATENT OFFICE HYDRoFLUoaIo acm ALKYLATIoN raocsss Frederick E. Frey,.Bartlesville, Okla., asslgnor to Phillips Petroleum Com Delaware pany, a corporation of Application August 10, 1943,. Serial No. 498,117

13 Claims. (Cl. 26o-683.4)

rivatives of such hydrocarbons, such as phenols. acids, ethers, etc.

An understanding of a preferred embodiment .of this invention may be facilitated by reference to the accompanying exemplifying drawing,

which is a schematic flow-diagram of one specific arrangement of equipment for practicing the inquent treating steps to form hydrofluoric acid, i

which is corrosive, and because they represent an undesirable consumption of the catalyst. Furthermore, in the hydrotluoric acid alkylation of isoparaiilns, the feed usually contains normal parafiins, which must eventually be separated from the alkylation effluent and must be removed from the alkylation system. Utilization of such Vnormal parafiins other than as diluents in connection with the alkylation of isoparains is desirable.

An object of this invention is to improve hydrofluoric acid alkylation of paraiiins.

A further object of my invention is to alkylate organic compounds.

Another object of this invention is to reduce catalyst consumption in alkylations of organic compounds catalyzed by hydrogen fluoride.

Other objects and advantages will be apparent from the accompanying disclosure and discussion.

In accordance with one specific embodiment of the present invention, an isoparafiin is alkylated with an olefin in the presence of hydroiiuoric acid; the reaction mixture is separated into two liquid phases; the hydrocarbon phase is freed from hydroiiuoric acid by azeotropic distillation; the acid-free hydrocarbon phase is fractionated into an unreacted-isoparaiiin fraction, a normalparamn fraction, and an alkylate fraction; the isoparaiiln fraction, together with its content of organic fluorine compounds, is recycled to the alkylation step; the other two fractions, together or separately, are defiuorinated by contact with a suitable solid material and are withdrawn from the process. The normal-paraiiin fraction is preferably dehydrogenated to furnish oleiins for the alkylation step. Novel features of this invention can also be applied to the alkylations of other organic compounds with olefins, such as normal paraiiins, cycloparaflins, aromatic hydrocarbons, and alkylatable, non-hydrocarbon deventlon.

A hydrocarbon alkylation feed enters alkylator I II through inlet II controlled by valve I2. It comprises an alkylata-ble hydrocarbon, usually a low-boiling isoparain such as isobutane or isopentane. an alkylant, usually one or more olefins of three to five carbon atoms per molecule. such as the butylenes, and relatively inert diluent materials, such as normal butane and some propane. Concentrated, or substantially anhydrous, hydrofiuoric acid enters alkylator I0 through inlet I3 controlled by valve I4 and is intimately mixed with the hydrocarbon feed by any suitable agitation means. The over-all mol ratio of iso-- paramn to olefin is preferably as high as is economically feasible; it is usually from 4:1 to 20:1, but may be as high as :1 if desired. The volume ratio of acid to hydrocarbon is ordinarily between 0.5 1 and 2.0:1, but higher or lower ratios may be maintained if desired. The temperature in alkylator I 0 is usually in the range of 'l5 to F. although the reaction may be conducted at higher or lower temperatures. The pressure is sufflcient to maintain all reactants in the liquid phase. but need not be unusually high. The time of residence of the reaction mixture in alkylator I0 is usually from 1 to 30 minutes; preferably it is from 5 to l5 minutes.

The reaction mixture is passed from alkylator I0 through conduit I5 and valve I6 to settler 20, in which the mixture is separated into two liquid phases by settling and/or centrifugation, aided if desired, by cooling. The heavier or hydrofluoric acid phase may be recycled directly to alkylator I0, as through conduit 2l controlled by valve 22; usually at least a part of the acid phase is passed through conduit 23 controlled by valve 24 to purification means, not shown, for purification before being recycled to alkylator I0.

The lighter or 'hydrocarbon phase is passed through conduit 25 controlled by valve 26 to azeotrope column 30, in which it is separated by fractional distillation into two fractions. The overhead fraction consists of a low-boiling, or azeotropic, mixture of hydrofluoric acidl and propane and/or isobutane. This fraction is passed through conduit SI controlled by valve 32, through condenser 33, and through conduit 34 toaccumulator 35, in which the fraction is separated by gravity into two liquid phases. The heavier phase, which comprises substantially anhydrous hydroiluoric acid, is recycled through conduit 36 controlled by valve 31 to alkylator I0. The lighter or hydrocarbon phase is returned as reilux to azeotrope columnel 30 through conduit 38 controlled by valve 38. The kettlel fraction from column 30, which comprises a substantially hydrogen iluoride-free hydrocarbon mixture and a minor proportion of organic uorine compounds, chiey alkyl iluorides, is passed through conduit 4| controlled by valve 42 to deisobutanizer 40. From deisobutanizer 4'0 an overhead fraction composed chieily of isobutane, propane, and a minor proportion of organic fluorine compounds is passed through conduit 43 controlled by valve 44 to depropanizer 50. From the depropanizer, an overhead fraction comprising chiefly propane is withdrawn through outlet 5| controlled by valve 52,

and a kettle fraction comprising chiefly isobutane and a minor proportion of organic iluorine compounds is recycled through conduit 53 controlled by valve 54 to alkylator I0. The organic iiuorine compounds accompanying the isobutane thus become available for alkylating isobutane in alkylator I0. Of course, if a negligible or small amount of propane is present in the overhead of the deisobutanizer 40, all or a substantial portion of this may be returned directly to alkylator I0 by bypassing depropanizer 50, by means not shown. By this means, a large part or all of any hydrogen fluoride formed by decomposition reactions in deisobutanizer 40 will be directly returned to alkylator i0 also.

The kettle fraction from deisobutanizer 40 is passed through conduit 45 controlled by valve 46 to debutanizer 00, from which an overhead fraction comprising chiefly normal butane and a minor proportion of organic iluorlne compounds is passed through conduit 0I controlled by valve 62 to defluorinator 90. This deiluorinator may be any suitable closed chamber containing a contact material, such as aluminum oxide, bauxite, chromium oxide, zirconia, calcium oxide, mag- 'nes'iumuoxida or other solid, porous metal oxide catalytically active 'for hydrogenation and dehydrogenation reactions. or nely divided nickel, iron or cobalt on a supporting material,that is capable of removing the organic iiuorine at temperatures in the range of approximately 150 to 550 F., as more disclosed in my hereinbefore mentioned copending application Serial No. 398,361 (Patent 2,347,945) The material undergoing deuorination may be in either the vapor or the liquid phase; in the present instance liquid-phase treatment is preferable. A generally suitable space velocity is 1 to 2 liquid volumes per hour.

The substantially uorine-free eiiluent from defluorinator 90 is passed through conduit 9i controlled by valve 02 to dehydrogenation means I 00, which comprises any suitable means for.

catalytic and/or noncatalytic dehydrogenation. In such apparatus the temperature is usually from 800 to 1300" F. and the pressure is preferably less than 200 p. s. i.

The eiiiuent from dehydrogenation means |00 is passed through conduitI i0| controlled by valve |02 to fractionation means IIO which usually comprises two or more fractionating columns. In fractionation means ||0 the hydrogenation eiiluent is separated into fractions, such as the following: (1) a fraction, comprising hydrogen and molecule, that is removed from the system as' through conduit H3 controlled by valve II4.

The kettle fraction from debutanizer 60 is passed through conduit 63 controlled by valve 64, to defluorinator 10, which is similar in construe--Y 4tion and operating conditions to defluorinator 30,l except that the temperature is preferably higher, in the range of 150 to 550 F. The contact material is preferably, although not necessarily, identical with that in deuorinator 90.

The vsubstantially fluorine-free eilluent from defiuorinator 10 is passed through conduit 1i controlled -by valve 12 to alkylate rerun column 00. An overhead light alkylate fraction, comprising hydrocarbons boilingin the motor-fuel range, is withdrawn through conduit 8| controlled by valve 82. A minor heavy alkylate fraction, comprising hydrocarbons boiling above the motor-fuel range, is withdrawn as a kettle product through conduit 83 controlled by valve 84. It is to be understood that the drawing is merely diagrammatic; any additional equipment, such as condensers, pumps, heat exchangers, etc.,

necessary for practicing the invention in any' particular installation may be supplied by any- Example In a continuous hydrofluorc acid alkylation system an over-all hydrocarbon feed approxi- A mating 47 weight per cent normal butane, 40

weight per cent isobutane, 5 weight per cent propane, and 8 weight per cent butenes is contacted with anhydrous hydrofluoric acid, at a temperature of about F., a gage pressure of 150 p. s. i., and a volume ratio of acid to hydrocarbon of 1:1, for a contact time of 10 minutes. The effluent mixture is passed to a settler in which the hydrocarbon phase is separated from the acid phase. The hydrocarbon phase is freed from dissolved hydrogen fluoride by distillation in an azeotrope column, and then it is distilled into several fractions in a series of fractionating columns. Propane is withdrawn from the system. Isobutane is recycled to the alkylation step; it contains alkyl fluorides corresponding to approximately 0.0300 weight per cent organically combined iluorine which is thus returned to the alkylation step for utilization of the alkyl fiuorides as alkylating agent and simultaneous liberation of the organic `fiuorine as hydroiluoricacid. The nor-z mal butane is defluorinated by contacting with emuent therefrom contains approximately 20 volume per cent olens, mostly butenes. The dehydrogenation Veiiluent is passed to a fractionating system, in which light gases are removed from the butenes. the propene, and the unreacted butane. These hydrocarbons are then recycled to the alkylation step, to become a part of the above over-al1 feed. A fraction of motor-fuel hydrocarbons is deiluorinated similarly and is withdrawn as a product of the process.

Because the invention may be practiced in f many ways other than as specifically described, and because many modiilcations will be apparent to anyone skilled in the art, the invention should not be restricted unduly by speciilc discussion presented herein.

I claim: 1. A process for the treatment of the hydrocarbon eilluent from a hydroiluoric acid alkylation step in which isobutane is alkylated in the tion step; passing said normal butane fraction to a rst deucrination means containing aluminum oxide and maintained at a temperature in the range 150-300 F. and effecting therein a removal of iluorine from said fraction; sub- `iecting the deiluorinated material so obtained to dehydrogenation; separating from the eilluent from said dehydrogenation a mixture comprising propene, butenes. and unreacted butane; passing said mixture to said alkylation step; passing said higher-boiling fraction to a second deuorination means containing aluminum oxide and maintained at a temperature in the range 150-500 F.; passing the substantially iluorinefree material so obtained to rerun means; and withdrawing from said rerun means a fraction boiling in the motor-fuel range and a fraction boiling above the motor-fuel range.

2. In a process for the alkylation oi alkylatable organic compounds by reaction with a low-boiling olen in the presence of a hydroiluoric acid catalyst, the improvement which comprises separating from eilluents of such an alkylation a low-boiling paraffin hydrocarbon fraction containing as impurities a minor amount of organic iluorine compounds formed during said alkylation, subjecting said paraiiin fraction to deiluorination to produce a substantially fluorine-free parailln fraction, dehydrogenating resulting iluorine-free parafflnic eiiluents of said deiluorination to form low-boiling olefins, and passing low-boiling oleflns so formed to said alkylation.

3. In a process for the alkylation o! alkylatable organic compounds by reaction with a low-bolling oleiln in the presence of accompanying lowboiling parafiln hydrocarbons and in the presence of a hydroiluoric acid catalyst, the improvement which comprises separating from eilluents of such an alkylation a low-boiling paraiiln hydrocarbon fraction containing as impurities a minor amount of organic iluorine compounds formed during said alkylation, subjecting said parafiln fraction to the action of a solid porous metal oxide catalytically active for hydrogenation and dehydrogenation reactions, at a reaction temperature and for a time such that extensive chemical changes in the parailin hydrocarbons in said fraction are not effected and such that the total eiiluent from said treatment is essentially iiuorine-free. dehydrogenating resulting iluorine-iree paraillnic ell'iuents of said deiluorination to form low-boiling oieilns, and passing low-boiling oleiins so formed to said alkylation.

4. In a process for the alkylation of alkylatable organic compounds by reaction with a low-boiling oleiln in the presence of a hydrotluoric acid catalyst. the improvement which comprises separating from eiliuents o1' such an alkylation a lowboiling paraflln hydrocarbon fraction containing as impurities a minor amount of organic iluorine compounds iformedl during said alkylation, subjecting said parafiin fraction to the action of a solid porous metal oxide catalytically active for hydrogenation and dehydrogenation reactions. at a. reaction temperature between about and 550 F. and for a time such that extensive chemical changes in the paraillns in said fraction are not ailected and such that the total eilluent from said treatment is essentially iluorine-free, dehydrogenating resulting fiuorine-free paraiiinic eftluents of said deiluorination to form low-boiling oleilns, and passing low-boiling olefins so formed to said alkylation.

5. 'I'he process of claim 4 wherein said porous metal oxide is alumina.

6. The process of claim 4 wherein said porous metal oxide is bauxite.

7. The process of claim 4 wherein said porous metal oxide is chromium oxide.

8. The process of claim 4 wherein said porous metal oxide is calcium oxide.

9. An improved process for reacting isobutane with normal butenes in the presence oi' a. hydroiluoric acid alkylation catalyst, which comprises passing to an alkylation zone a butane mixture and normal butenes, maintaining the contents of said alkylation zone under alkylation conditions in vthe presence of a hydroiluoric acid alkylation catalyst to react said butenes with isobutane contained in said butane mixture, removing from efiluents of said alkylation zone a hydrocarbon mixture free from free hydroiluoric acid, removing from said hydrocarbon mixture a fraction comprlsing unreacted isobutane and returning same to said alkylation zone, removing also from said hydrocarbon mixture a fraction comprising normal butane, said fraction being contaminated with organic iluorine compounds, subjecting said normal butane fraction to the action of bauxite lat a temperature between about 150 and 550" F. for a time such as to produce a substantially fluorine-free normal butane fraction, subjecting resulting fiuorine-free normal butane to catalytic dehydrogenation to produce normal butenes, and passing normal butenes so produced to said alkyla.. tion zone..

10. An improved process for reacting isobutane with normal butenes in the presence of a hydrofiuoric acid alkylation catalyst, which comprises passing to an alkylation zone a butane mixture and normal butenes, maintaining the contents of said alkylation zone under alkylation conditions in the presence of a hydrofluoric acid alkylation catalyst to react said butenes with isobutane contained in said butane mixture, removing from eilluents of said alkylation zone a hydrocarbon mixture free from free hydroiluoric acid, removing from said hydrocarbon mixture a fraction comprising unreacted isobutane and returning same to said alkylation zone, removing also from said `hydrocarbon mixture a fraction comprising normal butane. said fraction being contaminated with organic iluorine compounds, subiect- 2,4so,oas

7 ing said normal butane fraction to deiiuorination to produce a substantially iiuorine-tree normal butane fraction, subjecting. the resulting fluorineparaflin of three to tive carbon atoms per mole cule, in the presence ofhydroi'luoric acid as a catalyst, the steps comprising 'separating from the hydrocarbon effluent from the alkylation step a hydrogen fluoride-free traction containing said normal paraffin together with a minor proportion of organic iiuorine compounds, removing said iluorine compounds from said fraction, subjecting the fluorine-free fraction to dehydrogenation to convert normal paratlins contained therein to corresponding olefins, fractionating the eilluent from said dehydrogenation step" to separate a fraction comprising said olens, and recycling said lastnamed fraction to said alkylation step.

I. 12.V The process of claim 11 wherein said normal paramn is normal butane.

13. A process for the dehydrogenation of a low- .,-boillng paraln hydrocarbon material contamiquently subjecting the resulting iluorine-free paramn hydrocarbon material to dehydrogenation.

FREDERICK E. F'REY.

REFERENCES CITED The followingreferences are of record in the file of this patent:

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